The number of file descriptors received is not stored by vhost_user.c.
vhost_user_set_mem_table() assumes that memory.nregions matches the
number of file descriptors received, but nothing guarantees this:
for (i = 0; i < memory.nregions; i++)
close(pmsg->fds[i]);
Another questionable code snippet is:
case VHOST_USER_SET_LOG_FD:
close(msg.fds[0]);
If not enough file descriptors were received then fds[] contains
uninitialized data from the stack (see read_fd_message()). This might
cause non-vhost file descriptors to be closed if the uninitialized data
happens to match.
Refactoring vhost_user.c to pass around and check the number of file
descriptors everywhere would make the code more complex. It is simpler
for read_fd_message() to set unused elements in fds[] to -1. This way
close(-1) is called and no harm is done.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
2042cf7194